Thermosetting resin composition for high performance laminates

ABSTRACT

This invention concerns a thermosetting resin system that is useful in the manufacture of high performance prepreg, laminate and composite materials as well as the prepregs, laminates and composites made from the thermosetting resin composition.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. ProvisionalApplication Serial No. 60/337,362, filed Dec. 5, 2001, which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] (1) Field of the Invention

[0003] This invention concerns a thermosetting resin system that isuseful in the manufacture of high performance prepreg, laminate andcomposite materials as well as the prepregs, laminates and compositesmade from the thermosetting resin composition.

[0004] (2) Description of the Related Art

[0005] Plastics have certain mechanical and structural limitations thathave been lesssened by reinforcing the plastics with other components.Composites formed of various fibers embedded in a polymer resin matrixare especially useful, however, such compositions are susceptible toenormous physical property variations depending upon, for example, thenature of the fiber used, how the fiber is utilized, and the fibermatrix or binder. The uses for such composites range from airframes totennis rackets and from boat hulls to rocket motor casings, andlaminates for use, for example, as multilayer printed circuit boards inthe electronics industry.

[0006] Performance requirements for composites and laminate materialsare becoming more stringent. In the electronics industry, for example,high speed high frequency circuits require substrates with difficult toattain electrical properties, such as low dielectric loss and lowdielectric constant. Current composite materials do not meet theseelectrical requirements. In addition, other materials that may exhibitfavorable electrical properties do not possess the thermal propertiesrequired for composites and laminates. There exists a continuing need,therefore, for new composite materials having favorable thermal andelectrical properties, such as low dielectric loss and low dielectricconstant.

SUMMARY OF THE INVENTION

[0007] The invention provides a thermosetting resin composition usefulin the manufacture of high performance composite and laminate materials.The thermosetting resin composition comprises: at least one elastomer;at least one ester; and at least one flame retardant.

[0008] The invention also provides prepregs, laminates and compositesmanufactured from the disclosed thermosetting resin compositions.

DESCRIPTION OF THE CURRENT EMBODIMENT

[0009] The invention provides thermosetting resin compositions useful inthe manufacture of high performance composite materials, and toprepregs, laminates and composites manufactured therefrom. Thecompositions are particularly useful in the preparation of laminateshaving low dielectric constants and low dielectric loss (“low loss”).These electrical properties help solve signal speed and signal integrityproblems encountered with high speed analog digital applicationsmanufactured on laminates used with prior art resin systems. Laminatematerials manufactured with the thermosetting resin compositions of thepresent invention can have low and flat dielectric loss (≦0.005) and lowdielectric constant (≦3.4) at high frequency range of 5 GHz to 10 GHz,at comparatively low cost. “Flat dielectric loss” means that thedielectric loss is essentially constant over a range of frequencies. Thecompositions of this invention may have a dielectric loss as low as ≦about 0.005 over a frequency range of from 2 to 10 GHz. In addition tohaving favorable electrical properties, prepregs prepared from thecompositions of the invention are also non-tacky and easy to process.

[0010] The thermosetting resin composition includes the followingingredients: at least one elastomer; at least one ester; and at leastone flame retardant.

[0011] The elastomer used in the resin composition provides the desiredbasic mechanical and thermal properties of the cured resin and laminatesmade therefrom. Suitable elastomers are any elastomers that are known toone of skill in the art to be useable in electronic composites andlaminates. Preferably, the elastomer has a molecular weight in the rangeof about 2000 to about 20000. The elastomer can be used alone or incombination with other elastomer(s). Examples of useful elastomersinclude, but are not limited to, butadiene polymers, styrene butadienepolymers, acrylonitrile-butadiene copolymers, isoprene polymers,urethane elastomers, polyamides, and thermoplastic polymers in general,or mixtures thereof. One useful class of elastomers are styrenebutadiene divinyl benzene compounds (SBDVB). SBDVD compounds includemany unsaturated groups which allow them to crosslink with other resincompounds during resin curing. An example of an SBDVB compound is Ricon®250, a polybutadiene styrene divinylbenzene graft terpolymer availablefrom Sartomer (502 Thomas Jones Way, Exton, Pa. 19341). Another usefulelastomer is a maleinized polybutadiene styrene copolymer. An example ofa maleinized polybutadiene styrene copolymer is Ricon® 184MA6, availablefrom Sartomer. Elastomers are present in the thermosetting resincompositions of the invention in an amount from about 20% to about 60%,preferably from about 25 to about 35%, based on 100% by weight resinsolids of the composition.

[0012] The esters used in the resin compositions of the inventionimprove thermal and electrical properties of the resulting cured polymerand products made therefrom by reacting with unreacted elastomeringredients and by-products. The esters react with and consume excessstyrene in the preferred elastomers. The esters can be monomers,oligomers or polymers, such as polyesters. Preferably, the ester is anunsaturated ester. Also preferably the ester is styrenic based. Apreferred ester is an acrylic ester such as, but not limited to,dipentaerythritol pentaacrylate. Another preferred ester is anunsaturated polyester. A preferred unsaturated polyester is thecondensation reaction product of an unsaturated acid or anhydride, suchas maleic anhydride or fumaric acid, or an aromatic acid, with a lineardiol(s). The product of this condensation reaction preferably has thefollowing properties: about 0% free styrene content; average molecularweight of 4000-7000; and an acid value of 12-18. Esters may be presentin the thermosetting resin compositions of the invention in an amount offrom about 1% to about 15%, preferably from about 2 to about 8%, morepreferably from about 2% to about 6%, based on 100% by weight resinsolids of the composition.

[0013] The thermosetting resin compositions of this invention alsoinclude one or more flame retardants. Any flame retardant that is knownto be useful in resin compositions used to manufacture composites andlaminates may be used. Examples of useable flame retardants include, butare not limited to, halides of glycidyl etherified bifunctionalalcohols, halides of novolac resins such as bisphenol A, bisphenol F,polyvinylphenol or phenol, creosol, alkylphenol, catecohl, and novolacresins such as bisphenol F, inorganic flame retardants such as antimonytrioxide, red phosphorus, zirconium hydroxide, barium metaborate,aluminum hydroxide, and magnesium hydroxide, and phosphor flameretardants such as tetraphenyl phosphine, tricresyl-diphenyl phosphate,triethylphosphate, cresyldiphenylphosphate, xylenyl-diphenyl phosphate,acid phosphate esters, phosphate compounds containing nitrogen, andphosphate esters containing halides. Flame retardants are present in thethermosetting resin compositions of the invention in an amount of fromabout 5 to about 50%, preferably from about 10 to about 40%, based on100% by weight resin solids of the composition.

[0014] One preferred flame retardant is decabromodiphenylethane, whichhas the following structure:

[0015] Decabromodiphenylethane is commercially available, for example,from Albemarle Corporation (451 Florida St., Baton Rouge, La. 70801).The Albemarle product is sold as Saytex™ 8010. Decabromodiphenylethanehas been unexpectedly found to be easily dispersed in the resincomposition. Decabromodiphenylethane also has the unexpected andsynergistic result of significantly improving dielectric properties ofthe cured resin. As a result, the flame retardant is preferably includedin the resin composition of this invention in amounts far greater thanis necessary for a flame retardant in order to also enhance thedielectric properties of the cured resin. When decabromodiphenylethaneis used as the flame retardant, it is preferably present in thethermosetting resin compositions of the invention in an amount of fromabout 10% to about 50%, more preferably from about 20% to about 45%,based on 100% by weight resin solids of the composition.

[0016] One or more catalysts are optionally added to the thermosettingresin compositions of this invention in order to enhance the rate ofresin cure. The catalysts chosen may be any catalysts that are know tospeed up the rate of thermosetting resin cure. Preferred catalystsinclude peroxide catalysts that generate free radicals such as dicumylperoxide, or tert-butyl peroxybenzoate (commercially available from, forexample, Akzo-Nobel Polymer Chemicals LLC, Chicago, Ill. as Triganox-C).A more preferred catalyst is dicumyl peroxide. Catalysts are present inthe thermosetting resin compositions of the invention preferably in anamount of from about 2% to about 8%, more preferably from about 3% toabout 5%, based on 100% by weight resin solids of the composition.

[0017] One or more fillers can optionally be added to the thermosettingresin compositions of this invention to improve chemical and electricalproperties of the cured resin. Examples of properties that can bemodified with fillers include, but are not limited to, coefficient ofthermal expansion, lowering CTE, increasing modulus, and reducingprepreg tack. Non-limiting examples of useful fillers includeparticulate forms of Teflon®, talc, quartz, ceramics, particulate metaloxides such as silica, titanium dioxide, alumina, ceria, clay, boronnitride, wollastonite, and mixtures thereof. Preferred fillers includecalcined clay or fused silica. Another preferred filler is fused silica.Yet another preferred filler is silane treated silica. More preferably,the silane treated filler filler is fused silica treated with epoxysilane. When used, fillers may be present in the thermosetting resincompositions of the invention in an amount of from about 0% to about40%, preferably from about 5 to about 40%, based on 100% by weight resinsolids of the composition. Preferably the particle size of the filler isabout 20 μm to about 80 μm.

[0018] One or more solvents are optionally incorporated into thethermosetting resins of this invention in order to control resinviscosity and in order to maintain the resin ingredients in a suspendeddispersion. Any solvent known by one of skill in the art to be useful inconjunction with thermosetting resin systems can be used. Particularlyuseful solvents include methylethylketone (MEK), toluene, and mixturesthereof. The choice of solvent is often dictated by the resin curingmethod. When the resin is cured with hot air, then ketones are typicallythe preferred solvent. When the resins are IR cured, then a mixture ofketones and toluene is typically preferred. When used, solvents arepresent in the thermosetting resin compositions of the invention in anamount of from about 20% to about 50% as a weight percentage of thetotal weight of the composition.

[0019] The compositions of the invention can optionally include cyanateesters, which can improve thermal performance and provide goodelectrical properties. Cyanate esters can participate in thepolymerization and incorporate into the resin backbone. Various cyanateesters can be used, including, but not limited to2,2-Bis(4-cyanatophenyl)isopropylidene (available from Lonza Group underthe name Primaset® BADCy), bisphenol A cyanate ester (available fromCiba Geigy under the name AroCy™ B10), and mixtures thereof. When used,the cyanate ester(s) are present in the thermosetting resin compositionsin an amount about 2% to about 15%, preferably from about 4 to about 8%,based on 100% by weight resin solids of the composition.

[0020] One useful composition of this invention has the followingformulation, wherein amounts are based on 100% by weight resin solids ofthe composition.:

[0021] from about 25 to about 35 wt % of at least one elastomer;

[0022] from about 2 to about 8 wt % of at least one ester;

[0023] from about 20 to about 45 wt % of at least one flame retardant;

[0024] from about 5 to about 40 wt % of at least one filler; and

[0025] from about 3 to about 5 wt % of at least one catalyst.

[0026] The ingredients are suspended in a solvent in a ratio rangingfrom about 50-80 wt % solids to 50-20 wt % solvent and preferably about70 wt % solids to about 30 wt % solvent.

[0027] Other useful compositions of this invention have the followingformulations: HIGH PERFORMANCE ELECTRICAL LAMINATE FORMULATION RangePreferred Ingredients (wt %) Amounts(wt %)Styrene-Butadiene-Divinylbenzene 20-60 25-30 terpolymer from Sartomer(Elastomer) An unsaturated Polyester  2-15 5-7 Decabromodiphenylethane10-50 30-40 Calcined Clay or 20-40 23-28 Fused Silica (filler) Dicumylperoxide (catalyst) 2-5 4

[0028] The preferred ingredients are suspended in a solvent such astoluene, MEK or toluene/MEK in a ratio ranging from about 50-80 wt %solids to 50-20 wt % solvent and preferably about 70 wt % solids toabout 30 wt % solvent.

[0029] Yet other useful composition of this invention has the followingformulation, based on 100% by weight resin solids of the composition.:

[0030] from about 30 to about 35 wt % of RICON® 250 resin;

[0031] from about 2 to about 4 wt % of an unsaturated polyester;

[0032] from about 20 to about 25 wt % of decabromodiphenylethane;

[0033] from about 32 to about 38 wt % of fused silica; and

[0034] from about 5 to about 6 wt % of dicumyl peroxide.

[0035] The thermosetting resin compositions of this invention are usefulfor making prepregs in a continuous process. Prepregs are generallymanufactured using a core material such as a roll of woven glass webwhich is unwound into a series of drive rolls. The web then passes intoa coating area where the web is passed through a tank which contains athermosetting resin system of this invention, solvents and othercomponents. The glass web becomes saturated with the resin in thecoating area. The resin saturated glass web is then passed through apair of metering rolls which remove excess resin from the resinsaturated glass web and thereafter, the resin coated web travels thelength of a drying tower for a selected period of time until the solventis at least partially evaporated from the web. Second and subsequentcoatings of resin can be applied to the web by repeating these stepsuntil the preparation of the prepreg is complete whereupon the prepregis wound onto roll.

[0036] Lamination process typically entail a stack-up of one or moreprepreg layers between one or two sheets of conductive foil (such ascopper foil). Lamination methods and parameters may vary widely, and aregenerally well known to the person of ordinary skill in the art. In oneexample of a cure cycle, the stack is maintained at a pressure of about40 psi to about 900 psi and under a vacuum of about 30 in/Hg. The stacktemperature is raised from about 180° F. to about 375° F. over a periodof about 20 minutes. The stack remains at a temperature of about 375° F.for 75 minutes after which the stack is cooled from a temperature of375° F. to a temperature to 75° F. over a 20 minute period.

[0037] In another process for manufacturing laminates, thermosettingresins of this invention are premixed in a mixing vessel under ambienttemperature and pressure. The viscosity of the pre-mix is ˜600-1000 cpsand can be adjusted by adding or removing solvent from the resin. Afabric substrate, such as E glass, is pulled through a dip tankincluding the premixed resin, through an oven tower where excess solventis driven off and the prepreg is rolled or sheeted to size, layed upbetween Cu foil in various constructions depending on glass weave style,resin content & thickness requirements.

[0038] A thermosetting resin composition of the invention can also becoated directly on Cu substrate to form resin coated Cu using slot-dieor other related coating techniques.

[0039] The following examples are illustrative of various aspects of theinvention but do not serve to limit its scope.

EXAMPLES Example 1

[0040] Electrical and Thermal Properties

[0041] In this example, the electrical and thermal properties of aprepreg made with a composition of the invention were measured. Theingredients of the composition and their amounts are listed in Table 1.Toluene was used as solvent to provide a total solids content of about69%. TABLE 1 Amount Material (percentage of 100% solids) Ricon ® 250resin 31.91% an unsaturated polyester  2.90% Saytex 8010 flame retardant23.21% Fused silica filler 36.22% Dicumyl peroxide catalyst  5.76 %

[0042] The prepreg was prepared as described above. A 0.03″ woven glassfabric was used as the core material. The glass transition temperature(Tg) of the material was 100° C. Some thermal properties of the prepregare provided in Table 2. Some electrical properties of the prepreg areprovided in Table 3. The data show that the resin composition providesgood thermal properties and maximum Dk and Df values of 3.4 and 0.0043,respectively, at high frequency ranges of 2 GHz to 10 GHz. TABLE 2Thermal Properties Property Measurement CTE^(a) 0 to 100° C. 25-30ppm/m/° C. CTE 20 to 160° C. 60-100 ppm/m/° C. CTE RT to 288° C. approx180 ppm/m/° C. T-260^(b) >60 minutes T-288^(c) Approx 30-60 minutes

[0043] TABLE 3 Electrical properties. Property Measurement Permittivity(DK)_(max)  2 GHz (Bereskin method) 3.3  5 GHz (Bereskin Method) 3.3 10GHz (Bereskin Method) 3.4 Loss Tangent (DF)_(max)  2 GHz (Bereskinmethod) 0.004  5 GHz (Bereskin Method) 0.0042 10 GHz (Bereskin Method)0.0043

[0044] It is contemplated that various modifications may be made to thecompositions, prepregs, laminates and composites of the presentinvention without departing from the spirit and scope of the inventionas defined in the following claims.

What we claim is:
 1. A thermosetting resin composition comprising: atleast one elastomer; at least one ester; and at least one flameretardant.
 2. The composition of claim 1 wherein the at least oneelastomer comprises from about 20 wt % to about 60 wt %; the at leastone ester comprises from about 1 wt % to about 15 wt %; and the at leastone flame retardant comprises from about 5 wt % to about 50 wt %, eachas a percentage of the composition solids content.
 3. The composition ofclaim 1 wherein the at least one elastomer is selected from the groupconsisting of thermoplastic polymers, butadiene polymers, styrenebutadiene polymers, acrylonitrile-butadiene copolymers, isoprenepolymers, urethane elastomers, polyamides, astyrene-butadiene-divinylbenzene terpolymer, a maleinized polybutadienestyrene copolymer, and mixtures thereof.
 4. The composition of claim 1wherein the at least one ester is an unsaturated ester.
 5. Thecomposition of claim 1 further comprising at least one catalyst.
 6. Thecomposition of claim 5 wherein the at least one catalyst is a peroxidecatalyst.
 7. The composition of claim 5 wherein the at least onecatalyst comprises about 2 wt % to about 8 wt % as a percentage of thecomposition solids content.
 8. The composition of claim 1 wherein the atleast one flame retardant is decabromodiphenylethane.
 9. The compositionof claim 1 wherein the at least one elastomer is selected from the groupconsisting of a styrene-butadiene-divinylbenzene terpolymer, amaleinized polybutadiene styrene copolymer, and mixtures thereof. 10.The composition of claim 4 wherein the unsaturated ester is anunsaturated polyester.
 11. The composition of claim 6 wherein the atleast one catalyst is selected from dicumyl peroxide, tert-butylperoxbenzoate, and mixtures thereof.
 12. The composition of claim 1further comprising at least one filler selected from the groupconsisting of teflon, talc, quartz, ceramics, particulate metal oxides,silica, titanium dioxide, alumina, ceria, clay, boron nitride,wollastonite, and mixtures thereof.
 13. The composition of claim 12wherein the filler comprises about 5% to about 40% as a percentage ofthe composition solids content.
 14. The composition of claim 12 whereinthe filler is silane treated fused silica.
 15. A thermosetting resincomposition comprising: a polybutadiene styrene divinylbenzene graftterpolymer; an unsaturated polyester; decabromodiphenylethane; fusedsilica; and dicumyl peroxide.
 16. The composition of claim 15 whereinthe terpolymer comprises from about 30 wt % to about 35 wt %; thepolyester comprises from about 2 wt % to about 4 wt %; thedecabromodiphenylethane comprises from about 20 wt % to about 25 wt %;the fused silica comprises from about 32 wt % to about 38 wt %; and thedicumyl peroxide comprises from about 5 wt % to about 6 wt %, each as apercentage of the composition solids content.
 17. A prepreg comprising athermosetting resin composition and a core material, wherein thethermosetting resin composition comprises: at least one elastomer; atleast one ester; and at least one flame retardant.
 18. The prepreg ofclaim 17 wherein the at least one elastomer comprises from about 20 wt %to about 60 wt %; the at least one ester comprises from about 1 wt % toabout 15 wt %; and the at least one flame retardant comprises from about5 wt % to about 50 wt %, each as a percentage of the composition solidscontent.
 19. The prepreg of claim 17 wherein the at least one elastomeris selected from the group consisting of thermoplastic polymers,butadiene polymers, styrene butadiene polymers, acrylonitrile-butadienecopolymers, isoprene polymers, urethane elastomers, polyamides, astyrene-butadiene-divinylbenzene terpolymer, a maleinized polybutadienestyrene copolymer, and mixtures thereof.
 20. The prepreg of claim 17wherein the at least one ester is an unsaturated ester.
 21. The prepregof claim 17 wherein the thermosetting resin composition furthercomprises at least one catalyst.
 22. The prepreg of claim 21 wherein theat least one catalyst is a peroxide catalyst.
 23. The prepreg of claim21 wherein the at least one catalyst comprises about 2 wt % to about 8wt % as a percentage of the composition solids content.
 24. The prepregof claim 17 wherein the at least one flame retardant isdecabromodiphenylethane.
 25. The prepreg of claim 17 wherein the atleast one elastomer is selected from the group consisting of astyrene-butadiene-divinylbenzene terpolymer, a maleinized polybutadienestyrene copolymer, and mixtures thereof.
 26. The prepreg of claim 20wherein the unsaturated ester is an unsaturated polyester.
 27. Theprepreg of claim 22 wherein the at least one catalyst is selected fromdicumyl peroxide, tert-butyl peroxbenzoate, and mixtures thereof. 28.The prepreg of claim 17 wherein the thermosetting resin compositionfurther comprises at least one filler selected from the group consistingof teflon, talc, quartz, ceramics, particulate metal oxides, silica,titanium dioxide, alumina, ceria, clay, boron nitride, wollastonite, andmixtures thereof.
 29. The prepreg of claim 28 wherein the fillercomprises about 5% to about 40% as a percentage of the compositionsolids content.
 30. The prepreg of claim 28 wherein the filler is silanetreated fused silica.
 31. The prepreg of claim 17 wherein the corematerial comprises a woven glass web.
 32. A prepreg comprising athermosetting resin composition and a core material, wherein thethermosetting resin composition comprises: a polybutadiene styrenedivinylbenzene graft terpolymer; an unsaturated polyester;decabromodiphenylethane; fused silica; and dicumyl peroxide.
 33. Theprepreg of claim 32 wherein the core material comprises a woven glassweb.
 34. A laminate comprising one or more prepregs and one or moresheets of conducting foil, wherein the one or more prepregs comprises athermosetting resin composition and a core material, and wherein thethermosetting resin composition comprises: at least one elastomer; atleast one ester; and at least one flame retardant.
 35. The laminate ofclaim 34 wherein the one or more prepregs and the one or more sheets ofconducting foil are alternately stacked.
 36. The laminate of claim 34wherein in the thermosetting resin composition, the at least oneelastomer comprises from about 20 wt % to about 60 wt %; the at leastone ester comprises from about 1 wt % to about 15 wt %; and the at leastone flame retardant comprises from about 5 wt % to about 50 wt %, eachas a percentage of the composition solids content.
 37. The laminate ofclaim 34 wherein the at least one elastomer is selected from the groupconsisting of thermoplastic polymers, butadiene polymers, styrenebutadiene polymers, acrylonitrile-butadiene copolymers, isoprenepolymers, urethane elastomers, polyamides, astyrene-butadiene-divinylbenzene terpolymer, a maleinized polybutadienestyrene copolymer, and mixtures thereof.
 38. The laminate of claim 34wherein the at least one ester is an unsaturated ester.
 39. The laminateof claim 34 wherein the thermosetting resin composition furthercomprises at least one catalyst.
 40. The laminate of claim 39 whereinthe at least one catalyst is a peroxide catalyst.
 41. The laminate ofclaim 39 wherein the at least one catalyst comprises about 2 wt % toabout 8 wt % as a percentage of the composition solids content.
 42. Thelaminate of claim 34 wherein the at least one flame retardant isdecabromodiphenylethane.
 43. The laminate of claim 34 wherein the atleast one elastomer is selected from the group consisting of astyrene-butadiene-divinylbenzene terpolymer, a maleinized polybutadienestyrene copolymer, and mixtures thereof.
 44. The laminate of claim 38wherein the unsaturated ester is an unsaturated polyester.
 45. Thelaminate of claim 40 wherein the at least one catalyst is selected fromdicumyl peroxide, tert-butyl peroxbenzoate, and mixtures thereof. 46.The laminate of claim 34 wherein the thermosetting resin compositionfurther comprises at least one filler selected from the group consistingof teflon, talc, quartz, ceramics, particulate metal oxides, silica,titanium dioxide, alumina, ceria, clay, boron nitride, wollastonite, andmixtures thereof.
 47. The laminate of claim 46 wherein the fillercomprises about 5% to about 40% as a percentage of the compositionsolids content.
 48. The laminate of claim 46 wherein the filler issilane treated fused silica.
 49. The laminate of claim 34 wherein theone or more sheets of conducting foil are copper foil.
 50. A laminatecomprising one or more prepregs and one or more sheets of conductingfoil, wherein the one or more prepregs comprises a thermosetting resincomposition and a core material, and wherein the thermosetting resincomposition comprises: a polybutadiene styrene divinylbenzene graftterpolymer; an unsaturated polyester; decabromodiphenylethane; fusedsilica; and dicumyl peroxide.